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The words in our glossary are arranged alphabetically.
Select a letter from above to jump directly to the letter
with which your word begins.

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adjacent angles - two angles that share a vertex and a common side between them but have no interior points in common.

algorithm - a step-by-step procedure for carrying out computation.

alternate angles - two angles that are in opposite locations when lines are cut by a transversal. If the angles are between the lines, they are called alternate interior angles; if they are outside the lines, they are called alternate exterior angles. If the lines are parallel, the alternate angles are congruent.

area - The extent of a planar region or of the surface of a solid measured in square units.

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bias - A statistical sampling or testing error caused by systematically favoring some outcomes over others.

bisector of an angle - a segment or ray that divides an angle into two congruent angles.

bisector of a line segment - a point, segment, ray, or line that divides a line segment into two congruent segments.

box-and-whiskers plot - a type of graph used in data management particularly useful in showing the spread of the distribution of the data.

broken-line graph - a type of graph used in data management where the data points are joined by line segments. Also called simply a line graph.




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capacity - The maximum amount a container holds, usually measured in litres.


census - When information is gathered from all people in the population, the activity is called a census. Polls or surveys are a method of collecting data by asking people to give their answers to a set of questions.

chord - a segment joining two points on a circle.

circle graph - a graph of statistical data where a circle is subdivided into regions that represent the percent of the total.

complementary angles - two angles whose measures total 90 degrees.

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circumference - The distance around (perimeter of) a circle.

compound event - the outcome of a probability experiment that involves more than one object. E.g.: when you roll two dice and the result is a 5 on one and a 2 on the other, this is a compound event.

congruent - figures that have the same size and same shape.

congruent angles - angles that have the same measure.

congruent polygons - plane figures that are the same size and shape.

corresponding angles - angles that have the same relative positions. In parallel lines corresponding angles are congruent.







data - Facts and opinions from which conclusions can be drawn.

dependent events - when determining probability those events whose outcomes affect each other.

diameter - A chord that passes through the centre of a circle.

displacement - When an object is dropped into fluid, the fluid is displaced (moved) to make room for the space that the other object requires.  

edge - the line segment where two faces of a polyhedron meet

equiangular or equilateral triangle - see regular polygon.

estimation - determining an approximate amount, value, or size of something. Quantitative estimation is determining the approximate number of items in a group. Computational estimation is determining the approximate result to an arithmetic calculation. Measurement estimation is determining the approximate length, perimeter, area, volume, or other measurement of a geometric figure.

Euler's formula - a formula relating the number of vertices (V), faces (F) and edges (E) of a polyhedron. V + F - E = 2

event - one or more outcomes of a probability experiment.

experimental probability - the ratio of the favorable outcomes to the total outcomes in an experiment. e.g.. the experimental probability of drawing a 10 of spades from a deck of cards is 1:2.

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face - any of the flat sides of a polyhedron

frequency diagram - used in statistics as a method of recording the data collected. A tally is often used in the frequency diagram to keep track of the number of times something occurs.

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histogram - a type of statistical graph that uses bars, where each bar represents a range of values and the data are continuous.
isosceles - a polygon with two sides equal in length. Usually used to refer to either a triangle or a trapezoid.


length -The measurement of the extent of something along its greatest dimension: the length of the boat.

line graph - see broken line graph

line of symmetry - a line that divides a figure into two parts, each a mirror image of the other.


mass - The measurement of the amount of matter in an item.

mean - in statistics, the measure of central tendency calculated by adding all the values and dividing the sum by the number of values. (Often referred to as the average.)

- the measure of central tendency that is in the middle when the values are arranged in order of size. If there is an even number of data items, the median is the mean of the middle two.
of a triangle
- a line segment from any vertex of a triangle to the midpoint of the opposite side.

mode - the value that appears most frequently in a set of data.

net - a plane figure obtained by opening and flattening a 3-D object, or a 2-D pattern for a 3-D object.

observation - The act of noting and recording something, such as a phenomenon, with instruments.

obtuse triangle - a triangle with one obtuse angle.

odds - the probability that an event will occur compared with the probability of its not occurring.


parallelogram - A quadrilateral with opposite sides parallel.

perimeter - The distance around an object.

pi (3.14) - The ratio of the circumference to the diameter (C/d) of any circle.

polygon - a closed figure made up of line segments.

polyhedron - a 3D object that has polygons as its faces. The intersection of any two faces forms an edge.

population - Refers to the entire group about which data are being collected.

prism - a geometric solid with two bases that are congruent, parallel polygons, and all other faces are parallelograms. It is referred to as a right prism if the faces are rectangles. It is named according to the shape of its bases; e.g.: triangular prism.

protractor - a half circular device subdivided into 360 equal parts and used for measuring angles.

pyramid - a geometric solid with one base that is a polygon and all other faces are triangles with a common vertex.

Pythagorean Theorem in any right triangle, the square of the length of the hypotenuse equals the sum of the squares of the other 2 sides.

questionnaire - A form containing a set of questions, especially one addressed to a statistically significant number of subjects as a way of gathering information for a survey.

radius - The distance from the centre of a circle to any point on the circle.

random sample - Is a sample drawn in such a way that every member of the population has an equal chance of being chosen. Random sampling is often used in taking surveys when it is not feasible to survey every possible person.

range - in statistics, the difference between the least and the greatest values in a set of data. In more advanced statistics, it is considered the number of values between the greatest and the least, inclusive, and is calculated by the formula: range = greatest - least + 1.

reflection (flip) - a transformation of a geometric figure that results in a mirror image of it. The object and the image are equal distance from the line of reflection.

reflex angle - an angle whose measure is between 180 degrees and 360 degrees

research - Scholarly or scientific investigation or inquiry.

rhombus - a parallelogram with all sides equal in length

rotation (turn) - a transformation of a figure in which the image is formed by turning the figure about a fixed point called the centre of rotation. The centre may be inside or outside the figure.







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sample - A set of elements drawn from and analyzed to estimate the characteristics of a population. Also called sampling.

sample size - The number of items in a sample.

scale factor - The ratio of a distance measured on a scale drawing to the corresponding distance measured on the actual object.

scalene triangle - a triangle with all sides of different lengths.

secant of a circle - a line that intersects a circle in two points

similar polygons - polygons that have the same shape but not necessarily the same size.

simplest form - fraction is in simplest form if both its numerator and denominator are whole numbers and their only common factor is 1.

stem and leaf plot - in statistics, a way of recording, organizing and displaying numerical data so that the original data remains intact.

supplementary angles - two angles whose measures total 180 degrees.

surface area - The sum of the areas of all the faces, including the bases, of a 3-D object.





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tessellate - the repeated use of geometric figures to completely fill a plane without gaps or overlapping.

theoretical probability - probability that is determined on the basis of reasoning, not through experimentation. E.g.: because a regular die has 6 sides, the theoretical probability of tossing a 3 is 1/6.

translation (slide) - an exact duplication of a geometric figure formed by moving each point in the figure the same distance and in the same direction.

transversal - a line that intersects two or more lines in the same plane

trapezoid - a quadrilateral with exactly one pair of parallel lines.


vertex (plural: vertices) - the point of intersection of two rays that form an angle, two sides of a polygon, or two edges of a solid.

vertically opposite angles - two angles formed by the intersection of two lines. They share a common vertex but no sides or interior points.

volume -The amount of space occupied by a three-dimensional object or region of space, expressed in cubic units. Or, The capacity of such a region or of a specified container, expressed in cubic units.

weight - The measurement of how heavy an item is; The force with which a body is attracted to Earth or another celestial body, equal to the product of the object's mass and the acceleration of gravity.